U.S. patent number 8,466,789 [Application Number 12/733,391] was granted by the patent office on 2013-06-18 for method for theft recognition on a photovoltaic unit and inverter for a photovoltaic unit.
This patent grant is currently assigned to Fronius International GmbH. The grantee listed for this patent is Thomas Muhlberger, Roland Protsch. Invention is credited to Thomas Muhlberger, Roland Protsch.
United States Patent |
8,466,789 |
Muhlberger , et al. |
June 18, 2013 |
Method for theft recognition on a photovoltaic unit and inverter
for a photovoltaic unit
Abstract
The invention relates to a method for recognition of the theft
of at least one solar module (5) on a photovoltaic unit with an
inverter (1) an intermediate circuit (3), a DC-AC converter (4), at
least one solar module (5) connected via connector lines (19) and a
control device (8). A signal unit (19) which can be connected to
the connector lines (9, 10), for generating and transmitting an
electrical signal and a device for measuring and analyzing the
signal received from the at least one solar module (5) are provided
such that conclusions can be drawn about the theft of a solar
module (5) from the received signal. According to the invention,
reliable recognition of theft of a solar module (5) can be achieved
by designing the signal unit (19) for generating varying electrical
signals.
Inventors: |
Muhlberger; Thomas (Marchtrenk,
AT), Protsch; Roland (Roitham, AT) |
Applicant: |
Name |
City |
State |
Country |
Type |
Muhlberger; Thomas
Protsch; Roland |
Marchtrenk
Roitham |
N/A
N/A |
AT
AT |
|
|
Assignee: |
Fronius International GmbH
(Pettenbach, AT)
|
Family
ID: |
39970886 |
Appl.
No.: |
12/733,391 |
Filed: |
August 26, 2008 |
PCT
Filed: |
August 26, 2008 |
PCT No.: |
PCT/AT2008/000301 |
371(c)(1),(2),(4) Date: |
February 26, 2010 |
PCT
Pub. No.: |
WO2009/026602 |
PCT
Pub. Date: |
March 05, 2009 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20100207764 A1 |
Aug 19, 2010 |
|
Foreign Application Priority Data
|
|
|
|
|
Aug 29, 2007 [AT] |
|
|
1350/2007 |
|
Current U.S.
Class: |
340/571; 136/244;
340/568.1; 340/533; 340/531; 136/243; 340/568.2 |
Current CPC
Class: |
G08B
13/1418 (20130101); H01L 31/02021 (20130101); Y02E
10/563 (20130101); H02J 3/381 (20130101); Y02E
10/56 (20130101); H02S 50/10 (20141201); H02M
3/38 (20130101); H02J 2300/24 (20200101); H02J
3/383 (20130101) |
Current International
Class: |
G08B
13/14 (20060101); G08B 1/08 (20060101); H02N
6/00 (20060101); H04Q 1/30 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
94 11 783 |
|
Feb 1995 |
|
DE |
|
101 36 147 |
|
Feb 2003 |
|
DE |
|
101 61 480 |
|
Jul 2003 |
|
DE |
|
0584540 |
|
Mar 1994 |
|
EP |
|
2 286 475 |
|
Aug 1995 |
|
GB |
|
2000-164906 |
|
Jun 2000 |
|
JP |
|
WO 2007/048421 |
|
May 2007 |
|
WO |
|
WO 2008/043814 |
|
Apr 2008 |
|
WO |
|
WO 2008/046370 |
|
Apr 2008 |
|
WO |
|
Other References
European Search Report dated Sep. 26, 2012 in the corresponding
European Patent Application 08782829.9 with an English translation
of relevant parts. cited by applicant .
Austrian Office Action dated May 30, 2008 with English translation
of relevant parts. cited by applicant .
International Search Report. cited by applicant.
|
Primary Examiner: Mehmood; Jennifer
Assistant Examiner: Mahase; Pameshanand
Attorney, Agent or Firm: Collard & Roe, P.C.
Claims
The invention claimed is:
1. A method for theft recognition of at least one solar module (5)
on a photovoltaic unit, said solar modules (5) being connected in
normal mode via connector lines (9, 10) to at least one inverter
(1), with the voltage of the solar modules (5) being monitored, and
in a monitoring mode, when a defined voltage of the solar modules
(5) is measured, an electric signal is generated and applied to at
least one of the connector lines (9, 10) of the solar modules (5),
and the signal received by the at least one solar module (5) is
measured and analyzed to assess a theft, wherein in monitoring mode
a signal unit (19) integrated in an inverter (1) is activated by a
control device (8) of the inverter (1), and wherein electric
signals differing in form and amplitude are sent by the signal unit
(19) in succession to the at least one solar module (5), with that
electric signal, which causes a useful received signal when the
solar modules (5) are present, depending on the respective type of
solar module (5), being selected as a reference signal for
assessing a theft.
2. The method according to claim 1, wherein in monitoring mode the
solar modules (5) are being disconnected from the at least one
inverter (1) by a switchover device (11).
3. The method according to claim 2, wherein the electric signal is
generated by a signal unit (19) integrated in the switchover device
(11).
4. The method according to claim 3, wherein for activating the
switchover device (11) a starting signal is transmitted from the
control device (8) to the switchover device (11).
5. The method according to claim 4, wherein the connection of at
least one connector line (9, 10) to the at least one inverter (1)
is interrupted by at least one switchover means (16, 17) and at
least one of the connector lines (9, 10) is being connected to the
signal unit (19) by at least one switchover means (16, 17) when the
switchover device (11) is being activated.
6. The method according to claim 3, wherein the form and amplitude
of the electric signal are generated by the signal unit (19)
depending on the type of the solar module (5).
7. The method according to claim 6, wherein together with the
starting signal information about the type of the solar modules (5)
is transmitted and wherein depending on the type of the solar
modules (5) a corresponding electric signal is being generated by
the signal unit (19).
8. The method according to claim 1, wherein as an electric signal a
DC voltage signal or AC voltage signal is being applied between the
connector lines (9, 10).
9. The method according to claim 1, wherein as an electric signal
an HF signal is being applied between the connector lines (9, 10)
or between one of the connector lines (9, 10) and earth.
10. The method according to claim 1, wherein the electric signal is
sent in preferably periodical intervals of time.
11. The method according to claim 1, wherein a theft is detected
because of a sudden change in the received signal and an alarm
signal is generated.
12. The method according to claim 11, wherein the alarm signal is
transmitted to a data communication unit (15).
13. The method according to claim 12, wherein via the data
communication unit (15) a message is transmitted to a defined
receiver by a defined method of transmission.
14. An inverter (1) with an intermediate circuit (3), a DC-AC
converter (4), at least one solar module (5) connected via
connector lines (9, 10) in normal mode, and with a control device
(8), a control unit (18) for measuring the voltage of the solar
modules (5), providing a signal unit (19) which can be connected to
the connector lines (9, 10) for generating and transmitting an
electric signal in a monitoring mode, and a device for measuring
and analyzing the signal received by the at least one solar module
(5), so conclusions can be drawn about the theft of a solar module
(5) from the received signal, wherein the signal unit (19) is
integrated in the inverter (1) and connected to the control device
(8) of the inverter (1) and designed to generate electric signals
that differ in form and amplitude, so that electric signal, which
causes a useful received signal when the solar modules (5) are
present, depending on the respective type of solar module (5), can
be selected as a reference signal for assessing a theft in
monitoring mode.
15. The inverter (1) according to claim 14, wherein a switchover
device (11) for disconnecting the solar modules (5) from the DC-DC
converter (2) and for connecting the solar modules (5) to the
signal unit (19) is provided.
16. The inverter (1) according to claim 15, wherein a control unit
(18) for activating the switchover device (11) and the signal unit
(19) is provided.
17. The inverter (1) according to claim 15, wherein at least one
switchover means (16, 17) is arranged within the switchover device
(11).
18. The inverter (1) according to claim 17, wherein at least one of
the switchover means (16, 17) is designed for connecting at least
one of the connector lines (9, 10) to the signal unit (19) when the
switchover device (11) is activated in monitoring mode and for
connecting at least one of the connector lines (9, 10) to the
inverter (1) when the switchover device (11) is deactivated in
normal mode.
19. The inverter (1) according to claim 16, wherein the control
unit (18) is connected to the control device (8) via a data bus
(12).
20. The inverter (1) according to claim 19, wherein a data
communication unit (15), which is connected to the data bus (12),
is provided for transmitting a message depending on a detected
theft of a solar module (5).
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is the National Stage of PCT/AT2008/000301filed on
Aug. 26, 2008, which claims priority under 35 U.S.C. .sctn.119 of
Austrian Application No. A 1350/2007 filed on Aug. 29, 2007. The
international application under PCT article 21(2) was not published
in English.
The invention relates to a method for recognition of the theft of
at least one solar module on a photovoltaic unit, said solar
modules being connected via connector lines to at least one
inverter, with an electric signal being generated and applied to at
least one of the connector lines of the solar modules, and the
signal received by the at least one solar module being measured and
analysed in order to assess a theft.
The invention also relates to an inverter with an intermediate
circuit, a DC-AC converter, at least one solar module connected via
connector lines, and a control device, providing a signal unit,
which can be connected to the connector lines, for generating and
transmitting an electric signal, and a device for measuring and
analysing the signal received by the at least one solar module, so
conclusions can be drawn about the theft of a solar module from the
received signal.
Photovoltaic units are used to convert solar radiation energy to
electric energy. For this purpose, solar modules, which produce a
DC voltage, and inverters, which convert the DC voltage to an AC
voltage, are required. The generated AC voltage can be fed to the
public electricity grid or to directly connected consumers.
Photovoltaic units with a high performance and a correspondingly
high number of solar modules are often mounted at outdoor sites. In
this case, the components of the photovoltaic units might be
subject to theft and/or removal by force, especially the expensive
solar modules.
While security devices such as fencings, CCTV systems, motion
sensors or the like are known, they often fail to give the desired
results. Moreover, such measures require relatively great efforts
to be installed, and animals, for instance, might cause
malfunctions.
Other devices use mechanical security means such as locks, sensors
or the like, which are fastened to the solar modules. A
disadvantage of these solutions is that additional assembly
procedures, such as applying additional cables, are required.
WO 2007/048421 A2, for example, discloses a circuit for a
photovoltaic unit which makes it possible to detect malfunctions in
the solar modules.
DE 101 61 480 A1 discloses a method and a device to monitor solar
modules by monitoring characteristic values for sudden changes.
DE 94 11 783 U1 describes an anti-theft protection system for
photovoltaic solar generators, wherein, in the event of the removal
of a solar cell, the voltage increases considerably, so an alarm
can be set off and the theft can be detected.
Finally, JP 2000-164906 A shows a device to detect the theft of
solar modules on a photovoltaic unit, in which a test current is
applied to the solar modules, so in case of a theft values below
this test current are being detected.
The objective of the present invention is to provide a method as
mentioned above and an inverter as mentioned above, which can be
used to effectively protect the solar modules on a photovoltaic
unit from theft.
Regarding the method, the objective of the invention will be
achieved by transmitting in succession signals differing from each
other in form and amplitude to the at least one solar module, and
selecting as a reference signal for assessing a theft that signal
which causes a useful received signal when the solar modules are
present.
By the method according to the invention, a removal of a solar
module can be detected effectively. The effort required is
relatively low.
By using electric signals that vary in form and amplitude, an
optimal electric signal for theft recognition can be selected for
the respective type of the solar module.
Preferably, the generation of the electric signal takes place
inside the inverter of the photovoltaic unit, so no additional
components have to be mounted. Another advantage is that the theft
recognition is not visible to a thief.
Advantageously the electric signal is automatically generated and
applied if at least one inverter does not generate AC. Thus, the
method for theft recognition is activated automatically at dusk
and/or during the night, when the solar modules do not produce any
voltage.
In order to detect the beginning dusk and/or the night,
advantageously the voltage of the solar modules is monitored.
Thereby, dawn can also be detected automatically and preferably the
theft recognition can be switched off automatically.
According to another feature of the invention, the solar modules
are provided to be disconnected from the at least one inverter by a
switchover device when a defined voltage of the solar modules is
measured. Thereby, it can be achieved that the solar modules are
disconnected from the inverter or the inverters and connected to
the device for theft recognition at night.
The electric signal is generated by a signal unit that is
preferably integrated in the switchover device, said signal unit
being activated by a control device of the inverter. Thereby, the
switchover device is independent from the inverter and/or can be
adjusted to the inverter and may be installed at a later time. The
normal operation mode of the inverter is not influenced by the
switchover device.
In order to activate the switchover device and the device for theft
recognition, the control device of the inverter preferably
transmits a starting signal to the switchover device.
Preferably, the connection of at least one connector line to the at
least one inverter is interrupted by at least one switchover means
and at least one of the connector lines is connected to the signal
unit by at least one switchover means, when the switchover device
is activated. The switching over makes it possible to form an
electric circuit of its own for the theft recognition, so it can be
operated independently from the actual function of the inverter.
Also, the switching over disconnects the electronic parts of the at
least one inverter from the electric signal for theft recognition
and therefore protects them.
If the type of the solar modules is unknown, different electric
signals can be sent to the at least one solar module in succession,
and that electric signal which causes a useful received signal when
the solar modules are present can be selected as the reference
signal. Thereby, the optimal signal for the respective type of
solar module can be detected automatically. According to this, a
calibration of the electric signal to the type of the solar modules
in use takes place. That way, an exchange of the solar modules for
a different type can be detected automatically as well.
Alternatively, information about the type of solar modules can be
transmitted together with the starting signal for activating the
theft recognition and the signal unit can generate a corresponding
electric signal on the basis of the type of solar modules and/or
the information. Thereby, the electric signal can be generated and
sent by the signal unit on the basis of the transmitted information
about the type of solar modules.
As an electric signal, a DC voltage signal or AC voltage signal
between the connector lines or a high frequency signal between the
connector lines or between one of the connector lines and "ground"
may be applied.
If the electric signal is sent in preferably periodical intervals
of time, the energy consumption can be kept at a very low level,
but nevertheless a theft of a solar module can be recognised
basically immediately.
Advantageously, a sudden change in the received signal leads to a
theft of a solar module being recognised, and an alarm signal is
generated.
In the process, the alarm signal can be transmitted to a data
communication unit and this data communication unit, for example,
can transmit a message to a defined receiver by a defined method of
transmission. In particular, a communication system that may be
provided within the inverter may be used, which will make it easier
to install components of the theft recognition at a later time.
The problem of the invention is also solved by an inverter as
mentioned above, wherein the signal unit is designed in such a way
that it can generate different electric signals.
Advantages of this and of the dependent claims can be understood
from the advantages mentioned above. In the same way, further
advantages of the invention can be understood from the following
description.
The present invention is described in greater detail by means of
the schematic drawings included.
Therein,
FIG. 1 is a schematic overview of an inverter of a photovoltaic
unit;
FIG. 2 is a detailed schematic design of a photovoltaic unit with
the theft recognition according to the invention in normal
operation mode;
FIG. 3 is a detailed schematic design of a photovoltaic unit with
the theft recognition according to the invention in monitoring
mode; and
FIG. 4 is a detailed schematic design of a photovoltaic unit with
the theft recognition according to the invention in monitoring mode
during a theft of a solar module.
As an introduction, it is noted that same parts of the example are
indicated by same reference numerals.
FIG. 1 illustrates the design of an inverter 1, more particularly
an HF inverter. As the individual components and/or assembly groups
and functions of inverters 1 are already known in the prior art,
they will not be discussed in detail hereinafter.
The inverter 1 includes at least one input DC-DC converter 2, an
intermediate circuit 3 and an output DC-AC converter 4. The input
DC-DC converter 2 is connected to an energy source 13 and/or an
energy generator, which is preferably composed of one or more solar
modules 5 that are connected in parallel and/or in series (see
FIGS. 2-4). The inverter 1 and the solar modules 5 are referred to
as photovoltaic unit and/or PV unit as well. The output of the
inverter 1 and/or the output DC-AC converter 4 can be connected to
a supply network 6, such as a public or private AC voltage network
or a multiple phase network, and/or at least one electric consumer
7, which constitutes a load. A consumer 7 may be, for example, a
motor, refrigerator, radio equipment etc. The consumer 7 may also
constitute a home power supply system. The individual components of
the inverter 1, such as the input DC-DC converter 2 etc., can be
connected to a control device 8 by a data bus 12.
Preferably, such an inverter 1 serves as a grid-connected inverter
1, the energy management of which is optimised for feeding the
supply network 6 with as much energy as possible. As is known in
the prior art, the consumers 7 are fed energy by the supply network
6. Of course, a plurality of inverters 1 that are connected in
parallel may be used as well. Thereby, more energy for operating
the consumers 7 can be provided.
The control device 8 and/or the controller of the inverter 1 is
constituted, for example, by a micro processor, micro controller or
computer. The control device 8 can be used for an appropriate
control of the individual components of the inverter 1, such as the
input DC-DC converter 2 or the output DC-AC converter 4, especially
the circuit elements arranged therein. The individual control
procedures for this are stored in the control device 8 by
corresponding software programmes and/or data or
characteristics.
The energy source 13 is connected to the inverter 1 by two
connector lines 9, 10 and provides a suitable DC voltage.
According to the invention these two connector lines 9, 10 are used
to send an electric signal through the energy source 13 and/or the
solar modules 5. As the energy source 13 and/or the solar modules
5, which are connected to the inverter 1, form an electric circuit,
the signal sent by the inverter 1 will be received again. Thus, an
analysis of the signal sent by the inverter 1 can reveal whether
the energy source 13 and/or a solar module 5 has been removed or
stolen.
Such a theft recognition is carried out only when the solar modules
5 do not provide a sufficiently high DC voltage for the inverter 1
to correspondingly convert to an AC voltage that the network can
use. In this case, the inverter 1 does not feed AC to the supply
network 6 any more. Thus, the inverter 1 starts or activates the
theft recognition at night and/or at dusk.
The method for the recognition of the theft of a solar module 5
according to the invention, involving the inverter 1 according to
the invention, is illustrated in the following FIGS. 2 to 4.
A switchover device 11 according to the invention is provided in
the inverter 1 for theft recognition. During normal mode of the
inverter 1, when it feeds energy to the supply network 6, the
connector lines 9, 10 are connected to the DC-DC converter 2 by the
switchover device, as illustrated in FIG. 2. Should the voltage of
the solar modules 5 decrease, as this is the case at nightfall, the
inverter 1 cannot feed any more energy to the supply network 6. In
this case, preferably, the switchover device 11 disconnects the
inverter 1 from the solar modules 5 in order to activate the theft
recognition according to the invention, as illustrated in FIG. 3.
For this, the connector lines 9, 10 are disconnected from the input
DC-DC converter 2 of the inverter 1, for example, by two switchover
means 16, 17. Hence, the connection between the solar modules 5 and
the inverter 1 is interrupted and the input capacitor of the
inverter 1, in particular, is disconnected, so it cannot be
destroyed by the electric signal for theft recognition. Henceforth,
the connector lines 9, 10 for the energy source 13 and/or the solar
modules 5 are connected to a signal unit 19 via connection lines 14
by the switchover device 11 and/or the switchover means 16, 17, as
illustrated in FIG. 3. Preferably, this interruption is triggered
by a starting signal which is, for example, transmitted from the
control device 8 of the inverter 1 to a control unit 18 of the
switchover device 11 via the data bus 12. Then the control unit 18
will cause the activation of the switchover means 16, 17.
Of course the switchover device 11 may include only one switchover
means, in which case only the voltage loss of one switchover means
has to be considered. Semiconductors, relays or similar members
could, for example, be used as switchover means 16, 17.
Should the connector lines 9, 10 be connected to, for example, two
inverters 1 in parallel, both inverters 1 are disconnected from the
solar modules 5 by their respective integrated switchover device 11
in order to activate theft recognition. Preferably, the inverters 1
are connected by a data bus 12, so the disconnection of the
inverters 1 occurs basically simultaneously. By the same token,
information about at which time which inverter 1 sends the electric
signal for theft recognition and/or which of the inverters 1
performs this function is exchanged preferably via the data bus 12.
This guarantees that only one electric signal for theft recognition
is sent at all and, thus, is not subject to interference.
According to FIG. 3, the inverter 1 has been disconnected from the
solar modules 5, so the method for theft recognition according to
the invention can be carried out. For this purpose, an electric
signal, which has been generated in the signal unit 19, is sent to
the solar modules 5 via the connection lines 14 and the connector
lines 9, 10 to verify the presence of all solar modules 5. The
signal unit 19 may be integrated in or connected to the control
unit 18 of the switchover device 11, and may, for example, be
constituted by a signal generator.
Preferably, the signal unit 19 can generate different electric
signals, which mainly differ from each other in their signal forms
and amplitudes. Consequently, the theft recognition, which is
dependent on the signal, is not restricted to certain types of
solar modules 5. Corresponding data for different types of solar
modules 5 may, for example, be stored in a memory of the control
unit 18, so the signal unit 19 can use it to generate a
correspondingly suitable electric signal. Now for the signal unit
19 to be able to generate the electric signal adjusted to the solar
modules 5 in use, said signal unit 19 has to know the type of the
solar modules 5. This can be detected by a number of
procedures.
Firstly, the type of the solar modules 5 can be set in the inverter
1 and/or the control device 8, or in the switchover device 11
and/or the control unit 18 when the PV unit is brought into
operation. On the basis of this setting, the signal unit 19
generates a corresponding electric signal for carrying out the
theft recognition by using the stored data.
In the event that the type of the solar modules 5 has not been set,
preferably all signal forms that can be generated from the stored
data will be generated and sent through the solar modules 5 via the
connector lines 9, 10 one after another. The very signal form that
the signal unit 19 receives again correctly and/or analysable will
be used for the theft recognition. Applicable criteria for a
correctly received signal form are preferably stored in a
memory.
Preferably, the signal forms described hereinafter are eventually
generated for theft recognition by the signal unit 19, said signal
forms being appropriately adjusted to the type of the solar modules
5. The signal form may be formed by a DC voltage signal or an AC
voltage signal with different amplitudes. As a signal form for a
certain type of solar modules 5, for example, a DC voltage with a
constant amplitude may be used. The DC voltage causes a
corresponding current to flow through the solar modules 5. This
signal form is suitable for solar modules 5 with integrated diodes,
which only allow forward current in accordance with the diodes. By
measuring and analysing the current that reaches the switchover
device 11 and/or the signal unit 19, a theft can be recognised.
An AC voltage signal with a certain frequency (high frequency, in
particular) and a constant amplitude may also be used as a signal
form. The generated signal is transmitted to the solar module 5 via
the connection line 14, the transmission line and the corresponding
connector line 9, 10, and received again via the other connector
line 10, 9 and the other connection line 14, which serves as a
reception line. This signal form is preferably used for solar
modules 5 that do not have diodes and thus allow current flow in
both directions. The switchover device 11 decides which direction
is used as current flow for theft recognition on the basis of the
received signal form, so a theft is recognised correctly.
Consequently, the current can again flow through the solar modules
5 to be measured and/or analysed by the switchover device 11 and/or
the signal unit 19.
Such an AC voltage signal may also be applied between one of the
connector lines 9, 10 and "ground". Accordingly, an AC voltage
signal with a suitable amplitude, such as 20 volt, is applied to
one of the connector lines 9, 10, so part of this AC voltage is
applied between an earthed mounting of the solar modules 5 and
"ground". The mounting and the solar modules 5 constitute a
capacitance, so the part of the AC voltage and/or the current
resulting from it is referred to as capacitive current. This
capacitive current can be measured between one of the connector
lines 9, 10 and "groung" of the switchover device 11, requiring the
switchover device 11 to be earthed. Any change in this capacitive
current might indicate a theft.
As the form of the signal received is changed by the capacitance, a
theft of the solar modules 5 can also be detected in a difference
between the received signal and the sent signal. In this case, the
AC voltage signal is applied between the connector lines 9, 10.
In the case of solar modules 5 that are arranged in parallel or in
series, the electric signal will divide itself substantially evenly
between the strings connected in parallel. The switchover device 11
and/or the signal unit 19 receive the total of all strings'
currents.
After the signal form for the theft recognition has been defined
corresponding to the type of the solar modules 5, this signal form
and the form of the signal that is normally (i. e. when all solar
modules are present) received are being stored and a kind of
calibration is carried out. The signal forms stored will serve as
reference values and/or values for comparisons for at least the
following night, so if the form of the received signals should
deviate from the reference value, a theft is reliably detected.
A change and/or deviation of the received signal form from the sent
signal form is mainly detected by recognising a change in the
current through the solar modules 5, as its resistance changes
because of missing solar modules 5. The change that occurs is
substantially sudden, as theft of one or more solar modules 5 from
the circuit causes the resistance to undergo a substantially sudden
change as well.
This case is illustrated by a lightning symbol in FIG. 4. Thereby,
the current caused by the electric signal will change accordingly,
which makes it possible to draw conclusions about the theft of one
or more solar modules 5 on the basis of a change in the current.
Detecting a sudden change of the received electric signal for the
detection of the theft of at least one solar module 5 is of
particular importance when using the variant described above,
according to which the capacitive current is measured. This is
because other influential factors such as a change in humidity,
temperature or the like cannot cause a sudden change in the
capacitive current. On the contrary, a sudden change in the current
measured can reliably be interpreted as being caused by the removal
of a solar module 5. In general, more than one solar module 5 are
removed at the same time, as preferably a number of solar modules 5
are connected in series to form what is known as a string. Now, if
at least one solar module 5 of a string is removed, this will lead
to a change in the resistance of the entire energy source 13 due to
removing the resistance of one string.
When detecting a theft by the switchover device 11 and/or the
signal unit 19, an alarm signal, which can be transmitted to a data
communication unit 15 of the inverter 1 via the data bus 12, can be
generated. The data communication unit 15 can produce an alarm
message, which is communicated to defined persons and/or
institutions by telephone, fax, e-mail or the like, or it can
activate a warning light, signal horn or the like in the vicinity
of the PV unit and/or a control centre. That way, a theft can be
detected early and, as the case may be, prevented.
If, especially during the night, no theft of solar modules 5 is
detected, the inverter 1 can be switched back to normal mode
according to FIG. 2. This switching is again done by the switchover
device 11, which monitors the voltage transferred by the solar
modules 5. Once this voltage exceeds a defined and/or adjustable
threshold value, the switchover means 16, 17 are being switched
over, so the connector lines 9, 10 are being connected to the input
DC-DC converter 2. At the same time, a corresponding signal is
transmitted from the control unit 18 of the switchover device 11 to
the control device 8 of the inverter 1 via the data bus 12, so
preferably the relevant hardware and software components can be
activated. The inverter 1 can thus return to feeding energy to the
supply network 6 and/or supplying the consumers 7 with energy.
During the theft recognition, the inverter 1 receives electric
energy from the supply network 6 or an energy storage. In order not
to exert substantial influence on the effectiveness of the inverter
1 by the energy required for this, the electric signal can be sent
in periodical intervals of time such as every second, every ten
seconds or the like. Such an energy-saving measure will make it
possible to maintain a substantially permanent theft recognition
nevertheless.
It should also be noted that the theft recognition according to the
invention is not dependent on the type of the inverter 1. Instead
of the HF inverter 1 used in the example, an inverter 1 with a 50
Hz transformer, a transformerless inverter 1 or a stand-alone
inverter may be equipped with the device for recognising the theft
of the energy source 13 and/or a solar module 5.
Even though the description above focuses mainly on solar modules 5
as energy sources 13, the present invention may be applied to other
energy sources 13 as well.
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